Serial Killings That Aren't
by Writing Fangirl for hire
Summary: Castle and Beckett are investigating what appear to be a series of strange unnatural serial killings. Dean and Cas are investigating the same killings, but they know what's going on. Will the police and the hunter and angel be able to work together to crack this case?
1. Chapter 1

_**I know I should be working on "With Love and Pie" (after all I have had hardly any pie in there) But I had this idea for a **__**Castle**__** and **__**Supernatural**__** crossover. Tell me how you like it! **__**Disclaimer:**__** I don't own either show or it's characters, although if I did Castle and Beckett would have gotten married by now, Cas and Dean would have too, Sam and Gabriel would be living together, and Crowley would be less hated because Lucifer would ruling Hell. Also, Lucifer would take good care of and love Adam, because nobody else remembers Adam.**_

Castle looked over at her, her brown hair was pulled into a bit fancier of a ponytail, her makeup was done meticulously, and she looked uncomfortable as hell. She was wearing a light grey, ruffled shirt with a black pencil skirt that hugged her hips and ass tightly, she was also wearing shoes that Esposito would describe as "over-achieving secretary" shoes. Kate had refused to wear a fancy dress to the meeting with the Governor and choose to wear formal business clothes instead.

Kate shuffled from foot to foot, glancing over at Castle every so often. He was dressed very well. His black suit made his hair look lighter, his purple tie made his blue eyes pop. Kate forced her eyes to the Governor and what he was saying. It was something about how "proud he was of the department and it's..." at this he looked at Castle who grinned cheekily at him, "help." Kate rolled her eyes at Castle's fake pout. If you asked Castle, he'd probably tell you that the department helps him, but that they just benefit from it more then he does.

Castle fake pouted and kept looking over at Kate to see if she noticed. She did and she rolled her eyes. Inside Castle was grinning from getting that response from her but he forced himself to keep pouting. That is he did until Kevin Ryan's phone went off. Kevin quickly got up and stepped out of the room; Castle was jealous, he wished he had an excuse not to be here. If the longing look on Kate Beckett's face as she looked at the door was anything to go off of, she didn't want to be here either.

It was a relief to Kate when Kevin stuck his head back in the door.

"Triple homicide, right up our alley. Looks like it matches the last group of homicides. Said there was something strange about the place, we need to get ready to go now," Kevin told Kate. She let out a sigh of relief before turning to the Governor.

"My apologizes Sir, my team and I have to go," then seeing the pleading look on Castle's face out of the corner of her eye, "Also I might need my... help's assistance." The Governor sighed.

"Go then, save the world my friend. Solving one homicide at a time," The Governor replied. As they were exiting the room Castle whispered to her,

"That was so cheesy."

"Sounds like something you would write, Castle," Kate teased. Castle pulled a bitch face, but it quickly turned into a considering look, "Seriously Castle?"

"_The man with the green Mohawk smiled at the inspect_or flirtatiously. _With a wink he said, 'Go save the world hot stuff, solving one murder at a time.'_ I could actually use that," Castle said cheerfully. Kate rolled her eyes at Castle.

"To the normal police it would look like serial killings, five different multiple homicides, all killed the same way, for the same reason as we know, but by different people," Dean explained to Bobby over the phone as he and Cas drove to the latest homicide site. He would have had Cas zap them there, but for the fact that the place was crawling with police and it would seem a little suspicious for them to just come walking up. As Dean parked the car as close to the yellow police as he could, Cas pick out his FBI badge. He actually picked up the very first badge he ever used. Agent Eddie Moscone of the FBI. Cas smiled at it fondly before sticking it in one of the pockets of his favorite trench coat. Dean turned off the car, grabbed his fraudulent ID and opened the car door. He and Cas got out and walked around to the front of the car. Instinctively Dean reached over and fixed Cas's tie. Cas smiled at him and started walking.

They had just ducked under the police tape when someone stopped them. Cas let Dean do the talking as he normally did and just sat there and smiled at all the right times. The policewoman didn't stand a chance. So instead of getting flustered with the two, she took them to her superior.

"This is Detective Beckett, you can talk to her," The policewoman introduced them after talking to the Detective. Then, as she was passing by Cas he felt something being pressed into his hand, "and this is my number so that you can talk to me," the woman finished flirtatiously. Cas stumbled, as he always did when someone flirted with him. Finally he just smiled at the woman and nodded.

"Ahem," Detective Beckett cleared her throat to get their attention, as they were both watching the policewoman's retreating figure, "I'm Detective Beckett as was previously mentioned, and you are?"

"I'm Thomas Anderson, Serial Homicide Expert. This is my partner, Special Agent Edward Moscone," Dean answered them. Beckett raised an eyebrow.

"Moscone? Eddie Moscone?" asked some man coming up behind the detective. Cas nodded in response.

"An unfortunate name choice it turned out. He got picked on as a kid. I know, I had to figure a way to get his ass out of some nasty situations in fourth grade," Dean said.

"Can you speak for yourself Special Agent Moscone?" Beckett asked. Cas raised an eyebrow at her.

"I fail to see how I would not be able to, Detective Beckett," Cas replied in an unnervingly even tone for his low and gravely voice, "I must ask you, are there any strange markings inside?" the detective looked surprised by his question, but Cas continued looking around as if that should be the most common question in the world.

"Yes," the man answered for her. Cas immediately turned his attention on the blue eyed man.

"And you are?" Cas asked, he sounded like nothing Dean hadn't heard him sound like in a long time, he sounded prim. Like he was above the man in front of him. He asked it like he was asking why there was a slug on the sidewalk.

"Richard Castle," the man answered irritatedly.

"What part of the department do you work in Mr. Castle?"

"I don't, um, I don't work for the department. I'm a consultant. Well actually I'm a writer, I just help the department on some cases," the man, Castle, answered uncomfortably. Castiel raised his eyebrows in a patronizing way.

"I see, good. I will be able to work with you then," Cas suddenly sounded amiable, like he had just invited you over for tea and crumpets. The surprise on Castle's face was quite evident, as was the confusion on the detective's face.

"Ed here doesn't like working with the local police," Dean tried to explain to Beckett.

"You, Beckett, I will need your full cooperation. Thomas and I are currently working on a group of serial killings. I assume that that is what you believe this is?" Cas stepped over to Beckett, looking her up and down before looking her evenly in the face, "You are dressed far to fancy for just a regular case. Or any case that you are not undercover for. Why?" Beckett looked taken aback by the question.

"Um, I had a meeting," she answered slowly, "I don't see how this is relevant."

"It isn't, not as far as the case goes. I was just stating that you look nice. I take it that you prefer dark jeans, a solid color undershirt and a black jacket, paired with comfortable boots," Castiel said confidently. Beckett raised her eyebrows.

"So you have a good fashion sense, is that supposed to mean something?" She asked. Dean snorts.

"Ed has a terrible fashion sense. The one time he decided to change up his wardrobe he picked ugly Christmas sweaters. I thought my eyes were going to burn out," Dean said.

"It doesn't mean anything Kathrine," Cas said, pulling a bitch face on Dean.

"Wha- how do you know my first name?" Beckett asked. Cas raised an eyebrow.

"You honestly think that someone like me hasn't heard of someone like you?" Cas asked in a seductively low and sweet voice, that almost made _Dean_ moan, "After all, you are _the_ Kate Beckett are you not?"

"Well yeah, I mean, um, unless there is another _the_ Kate Beckett," she replied, blushing. Cas smiled a sugary smile that made the detective stare at the ground.

"May I go and take a look at the symbols inside?" Cas asked her. Unlike how he first treated Castle, Cas acted with humble modesty now. Kate was nodding her head and leading Cas towards the big warehouse in front of them before Dean could blink.

"Are you sure your buddy doesn't like working with the police?" Castle asked, a twinge of jealousy was in his voice. Dean smiled.

"He only works with the hot ones," He replied, walking away from the man.


	2. Chapter 2

Kate Beckett stared at the strange man in the trench coat. He was closely inspecting one of the strange blood-drawn symbols that covered the room. His partner, Anderson, walked in with Castle trailing in his wake.

"What you think Ed?" Anderson yelled to him. Ed Moscone motioned for the man to come over.

"De- Tom, the markings are Enochian. But this is not human or demon blood."

"What type of blood is it?" Anderson asked his partner. The partner looked around, distressed.

"Tom, it is angel blood," Moscone sounded strained.

"Shit. Is this part of the mess you have upstairs?" Anderson asked. Moscone shook his head.

"Is this all code for something?" Kate asked finally. Moscone swung around to stare at her, "What is Enochian? And what do you mean Angel's and Demons?"

"Well, uh, gangs," Tom answered, scratching the back of his neck.

"Okay... so we are dealing with gangs now?" Castle asked. Moscone smiled sweetly.

"Richard, can I call you Richard? Two of these are very powerful gangs, Enochian is a code that the two gangs often use to communicate when they aren't warring; or to, when they are warring, send warnings. The Angels and the Demons love to use these smaller gangs, we prefer to call them humans cause it seems so fitting, to do some of their dirty work. In reward the humans often get to join the big gang."

"You said that the blood was angel blood. How can you tell?" Beckett asked.

"Ah, well..." Ed started.

"It's the shade of red it is," Tom interrupts to explain, "Ed's a wizard when it comes to color's. He can tell you the exact shade difference. That's why they always have us come investigate the gang killings. We were told this was an angel hit. As in angels making the hit... now we aren't so sure." Beckett nodded in response. It all seemed way too complicated to her.


	3. Chapter 3

"It's not actual blood," Anderson said, "Well it kinda is, but it's not. You see... ugh. I can't explain this. Ed?" Moscone shot his partner a face, that Kate couldn't read, before sighing.

"It is indeed blood. But it has something in it that we haven't been able to trace... Something that gives the difference. We think the demon blood might have a hint of sulfur mixed in, but we aren't sure. Do you understand?" Moscone asked, a look of hope on his face said that he really hoped she wouldn't ask anymore questions.

"No. But that's okay. What do we need to look for?" Kate answered. A look of relief washed over the two agents. Moscone looked around, suddenly his face twisted in confusion.

"Where are all the bodies?" He asked. Kate knit her eyebrows together in momentary confusion.

"There's only the two."

"No," Moscone said, suddenly he took off running towards the opposite end of the building. He started looking all over for something.

"There was only two!" Castle shouted to the man.

"There's never just two. They don't work like that. If there was just two here that means there's more somewhere else," Anderson explained.

"Is it possible that just once they did kill only two people?" Kate asked in a no nonsense tone. Anderson shook his head. Moscone came running up to him, breathing only slightly heavier.

"De-Tom, I need to make a call upstairs. There is something very wrong here," he told his partner. Thomas Anderson got a strange look on his face before nodding.

"Do what you have to do." The two men clasped each other's shoulders and shared a long look before Moscone broke the hold and started to walk away.

Suddenly there was a flash of light, close to the ruffling of feathers, and a man standing in front of Moscone.

"Hello Castiel," Micheal said. Cas looked up into Micheal's face.

"Now isn't a good time, brother," Cas said trying to push past the archangel. Micheal rolled his eyes.

"Never would be a good time for you." Cas kept trying to push past, "Where do you think you are going Castiel?" Micheal let Cas take a few steps away from him before throwing something at Cas's feet. Fire encircled him. Cas sighed. Turned around. And stared past Micheal to Detective Beckett, Richard Castle, and Dean. Beckett had a gun in her hand, Castle had this look on his face like he was trying to figure out what happened, and Dean's face was covered in terror.

"Sir, I don't know who you are but could you please step away from Agent Moscone?" Beckett yelled at him, aiming the gun. Micheal raised an eyebrow.

"A brave human you have here Castiel. But not very smart. I assume that you know why I am here brother?" Micheal asked.

"Micheal, what is going on? This was an angel battle, not a hit like you told Gabriel and I."

"They doubted Castiel. They were ready to rebel. I couldn't let that happen. You must understand," Micheal said earnestly.

"What about me? You never attacked me! Why them?" Cas was yelling now. The angel blade appeared in his hand.

"Cas..." Dean warned. Beckett looked at him.

" So, your names aren't really Thomas Anderson and Eddie Moscone?" Castle asked, eyes never leaving the brothers in the middle of the room.

"You have no idea how many people actually fall for that," Was all the Dean said to the writer.

"The Father gave us specific instructions concerning you, we had no choice. But these two we couldn't risk it with." Micheal's own angel blade was now in his hand. When a voice across the room called out to them.

"Well isn't this fabulous! A family gathering. Too bad Balthazar, Uriah, Luci, and Anna aren't here. Then we could have a real party then.:

"Gabriel," both Cas and Micheal said, turning to look at the other archangel. Suddenly Dean stepped forewards.

"What the hell is the trickster doing here?"

"Nice to see you too Dean-o. You're still your same annoying self, I see. How disappointing. How's little bro? Tell my favorite Moose that Tuesday would work better for me," Gabriel said to Dean before turning back to his brothers, "Alright Micheal, let Cassie go."

"He needs to understand why we did it."

"We?" Gabriel asked, "Who's we? Last time I checked I tried to get you to go out for strawberry ice cream, not to kill our brother and sister."

"You really told Castiel to come here?"

"Better believe it bucko. Thought there was something here he'd like to know. Love you big bro, but I gotta go." Gabriel snapped his fingers and a bucket of water appeared. Which he immediately dumped on the fire ring. Snapping his fingers again, he disappeared.

"Leave Micheal. We have nothing else to talk about," Cas said, his head falling to his chest. Micheal nodded and disappeared in a flurry of feathers. As soon as Micheal disappeared, Dean came running up to him and pulled him into a hug.

"Man this situations sucks balls. What do ya say we get outta here and go to a diner. You can get as many hamburgers as you want, on me," He said. Beckett grabbed his arm.

"So you lie to us about your identities, come in and tell us some tale about gangs, have some weird dudes that do magic tricks come in and deliver bad news, and you expect us to just let you leave? I don't think so. You're coming back with us to the station." Dean groaned, Cas just pressed his lips together and nodded. Dean hated police stations, the people always ask to many questions and they don't have pie.


	4. Chapter 4

_**Hey everyone! Just letting you know that I did not drop off the face of the earth or any other dimension, I've stupid ass busy this summer and very distracted. I'm also working on a Sabriel fic, another Destiel fic, and a Merthur fic to release... sometime. It seems like I've been working alot on them but they still aren't ready yet. To all of my supporters... thank you for being patient with me even and for reading my fics. You all mean a lot to me! I know what you're thinking, "Sure we do..." but for real, I love it when I get an email notifying me that someone favorited, review, or followed me or one of my stories. So thanks for doing so! Keep up the good work.**_

_**Write On,**_

**_WFFH._**

**_So without furthur ado, Allons-y!_**

* * *

Kate Beckett stared at the two men sitting in the questioning room. The blonde man, Dean, Winchester refused to be serious about anything and was being very uncooperative. The other one, who introduced himself as Castiel Winchester Novak, stared back at her through the one way glass. Unmoving, unemotional, the man barely blinked. Every so often Dean would lean over and whisper something to him, the mic would catch snippets of conversation. Something about another man, Sammy, angels and demons, and someone else named Gabriel.

Esposito peeked his head in.

"I got the file, the one guy we got in there is Dean Winchester, and man does he have a track record. Tons of cases of credit card fraud, impersonation of an officer of the law, disturbing the peace, assault, a few murder accounts which were later changed to manslaughter under the pretense of self defense, and quite a few reports of arson cases on here as well. The other guy we have nothing on. I mean absolutely nothing. The guy doesn't show up on any FBI records, he doesn't have an ID. With what we have on him, the guy doesn't exist," he said handing her the file. Kate nodded.

"The brothers? The ones that showed up in the warehouse, what about them?"

"No idea, Kevin's working on that now."

"Okay, I'm gonna go talk to them," Kate said, leaving the room.

Entering the questioning room, Kate noticed that Dean immediately stiffened around her. Castiel, however, watched her calmly.

"You have quite a FBI record Mr. Winchester," Kate commented. Dean smiled charmingly at her.

"Please, just call me Dean. Mr. Winchester was my father, and my father isn't around anymore. The only living Winchester who would let you get away with calling him Mr. is probably my brother," he said.

"I see, and how does your brother feel about your legal record?"

"Well considering he's got a very similar one, I'm sure he doesn't give a damn as long as it's not sitting in front of me while a hot detective goes through it." Dean was flirting with her. She stuck her tongue in her cheek and raised her eyebrow at him before turning to Castiel.

"And are you aware Mr. Novak, that according to what we found on you, which is nothing I might add, you do not exist?" She asked.

"Yes."

"Are you going to tell me your real name Mr. Novak?"

"I did, my name is Castiel."

"But not Castiel Winchester Novak?"

"No. I do not have a last name. But I figured you would want a last name. I just couldn't figure out whether I should use Dean's or Jimmy's."

"Who's Jimmy?"

"My- no one. Jimmy is no one, just a friend. From my child hood," Castiel stuttered.

"Are you lying to me?" Kate asked.

"Yes."

"Why?"

"Because I can not tell you the truth," Castiel answered matter of factly. Kate sighed.

"Listen Castiel, I want to help you. The only thing you've done wrong that we have found is impersonating an FBI agent. But if you can't tell me the truth then I'm going to have to assume that you've committed a much bigger crime," She said, giving him a smile. Castiel looked over at Dean then back at her.

"I will tell you everything you want to know if you let Dean go," He said.

"Cas..." Dean warned.

"No can do, he's got to much on him."

"I can explain everything. I will tell you everything you want to know, about myself and about Dean, if you let him go," Castiel continued.

"I'm sorry Castiel, but that's not how the law works," Kate said. Castiel nodded.

"I guess you don't want to know who the next target is," Castiel said, leaning back in his chair, crossing his arms.

"You're not playing this game with me."

"I know who's going to die next."

"I'm not falling for it Castiel," Kate insisted. She was curious though. Suddenly Castiel sat straight up in his chair and look at Dean. Dean raised an eyebrow.

"Detective Beckett, do you have a business card?"

"Yes... Why?" she asked as she opened her folder and grabbed one.

"May I see it?" Castiel asked. Kate handed it to him, he looked at it and smiled. Then he stood up, Dean did too. Kate quickly stood, confused.

"Detective Katherine Beckett, my name is Castiel, I am an Angel of the Lord, this is Dean Winchester he is a hunter of the supernatural. This serial homicide case you are working is actually a war between Heaven and Hell. If you are lucky, the Winchester's and I will get it all sorted out without your help and the homicides will stop. If you aren't lucky we might need your help, or the Apocalypse will happen. Preferably the former. Good day Detective, have fun trying to find us," Castiel said. After which he placed two fingers on Dean's forehead and the two of them disappeared. Kate's eyes went wide.

"What the hell?" She asked to no one in particular.


End file.
